Ole Herman Johannes Krag (1837 – 1916) was a Norwegian gun designer. He designed a wide range of firearms during his lifetime, but only two – the Krag-Petersson and the Krag-Jørgensen – were adopted by any armed forces. Less than 1,000 Krag-Petersson rifles were made for the Royal Norwegian Navy, while several hundreds of thousands Krag-Jørgensen rifles were made for the Danish, Norwegian and US armies.
Ole H J Krag was born in Vågå, Norway. He started his military career in January 1854. He became a Second Lieutenant in 1857 and a full Lieutenant in 1861. In 1866 he was ordered to Kongsberg Våpenfabrikk, the most important Norwegian weapons factory of its day.
Ole H J Krag constructed his first repeating rifle in 1868, which evolved into the Krag-Petersson (aided by Axel Petersson) by 1872. This, as well as his work in the armoury, gave him a thorough understanding of what requirements the Norwegian Army had to a rifle, allowing him to create the successful Krag-Jørgensen with the help of his good friend Erik Jørgensen.
In 1880 he was named director of the armoury. After the Krag-Jørgensen was accepted as the main rifle of the Norwegian Army, he was made a Lieutenant Colonel in 1894. He retired in 1902.